The present invention relates to a room temperature-curable organopolysiloxane composition or, more particularly, to a room temperature-curable organopolysiloxane composition which is quite satisfactory as an insulating material around contact points in electric and electronic instruments without the problem of unreliable electric contact in the contact points.
As is well known, various kinds of organopolysiloxane compositions are used as an insulating material around contact points in electric and electronic instruments, of which the most widely used ones are room temperature-curable organopolysiloxane compositions curable by the reaction with atomospheric moisture in consideration of convenience and workability in the use thereof.
The crosslink formation in these room temperature-curable organopolysiloxane compositions proceeds by the mechanism of a condensation reaction to produce a condensation product which is usually a compound readily dissipated into the atomosphere. Accordingly, the room temperature-curable organopolysiloxane compositions are classified in relation to the type of the condensation reaction or the condensation product produced thereby into deketonation type, dealcoholation type, deoximation type, decarboxylation type and deamination type producing a ketone, e.g. acetone, an alcohol, e.g. ethyl alcohol, an oxime, e.g. methyl ethyl ketoxime, a carboxylic acid, e.g. acetic acid, an amine, e.g. diethylamine, respecively.
These types of room temperature-curable organopolysiloxane compositions have their own advantages and disadvantages. For example, the compositions of the deoximation type, decarboxylation type and deamination type are not suitable for use as an insulating material around electric and electronic contact points because the gaseous condensation products produced by the crosslinking reaction are corrosive against metals to cause unreliableness in the electric contact in the electric circuits of, for example, motors and relays. Though free from the problems caused by the corrosive condensation product formed in the course of curing, the compositions of deketonation type and dealcoholation type are also not satisfactory as an insulating material around electric and electronic contact points because these compositions comprise an organopolysiloxane as the base component which necessarily contains a low-molecular fraction of the organopolysiloxane having volatility more or less and also comprise a low-molecular organosilane compound as a corsslinking agent so that the vapor of these low-molecular organosilicon compounds is decomposed by the sparks between the contact points to form silicon dioxide which is deposited on the surface of the contact points as an insulating material to cause disorder in the performance of the electric circuits for motors and relays.